Defrosting arrangement for a refrigerating coil



H. T. NOONE May 29, 1956 DEIFROSTING ARRANGEMENT FOR A REFRIGERATINGCOIL 2 Sheets-Sheet 1 Filed March 18, 1955 INVENTOR.

H. T. NOONE May 29, 1956 DEFROSTING ARRANGEMENT FOR A REFRIGERATING COILFiled March 18, 1955 2 Sheets-Sheet 2 INVENTOR. MA 77 WW BY UnitedStates Patent-O DEFROSTING ARRANGEMENT FORA REFRIGERATING COIL Howard T.Noone, Atlanta, Ga., assignor to Carrier Corporation, Syracuse, N. Y., acorporation of Delaware This invention relates to a defrostingarrangement for a refrigerating coil subject to the air of arefrigerated space maintained at temperatures below the freezing pointof water and to the method of defrosting the coil.

It is customary in low temperature refrigeration in which a space isrequired to be constantly maintained at temperatures below the freezingpoint of water to employ a refrigeration coil placed in the refrigeratedspace or in a position connected to the refrigerated space, and a fan topass air through the coil to supply cooled air to the refrigeratedspace. Under these conditions, of course, frost collects on the surfacesof the coil so that periodic defrosting is required to remove the frostfrom the coil.

It has been proposedheretofore to spray water from a spray panor spraynozzles over the surfaces of the coil to remove frost therefrom. In manycases, thisarrangement presented a diificult'problem for'frequently afilm-ofwater formed across the orifices of the spray nozzles or spraypan, the water freezing to clog or block the nozzles. Thus, whendefrosting of the coil was 'again required; it was impossibleto'spraywaterthereover because'the water could notpass through the orifices.

Under these circumstances-,it was necessary for the operator todiscontinue operation of the refrigeration system and enter therefrigerated space to clear the nozzle orifices of i'ce preventingpassage of'the defrosting mediu'msuch as water over the surfaces of thecoil. This is: disadvantageous not only because the operator is forcedto work at temperatures considerably below the' freezing point of water,but chiefly because during this extended shut down of therefrigerationsystem", temperatures 'in the refrigerated space mayrise toapoint-in which the food products stored therein are subject to spoilageas wellas permitting the formation of heavy layers of frost over thecoil which are extremely difiicult to remove. The

present invention provides a simple andhighly effective I means fordefrosting which obviates these disadvantages.

The present invention relates to the combination with 1 a refrigeratedspace ofa coil adapted for periodic defrosting, water, distributingmeans placed to distribute water over the coil to defrost thecoil, a fanto move air of the periodwhen the fan is inoperative, and compressed airsupply means connected to the watersupply linerfonsupplyinggcompressedair to the waterv distributing. means. to remove any water film formedacross-the distributing orifices.

This invention further relates to a method of defrosting a refrigeratingcoil adapted to cool a refrigerated space having in combinationtherewith a water supply line and spray nozzles for: distributing waterover the coil to remove frost therefrom, characterized by the steps ofspraying water over the coil to. remove the frost therefrom, then, whendefrosting is substantially completed, discontinuing the supply of waterto thespray nozzles draining thewater supply line and supplying.compressed air to the water supply line through the spray nozzlestoremove any water film formed across the orifices thereof.

The attached drawings illustrate a preferred embodiment of theinvention, in which' Figure 1 is adiagrammatic view of a refrigeratedspace embodying the present invention;-

Figure 2 is a view-in-elevatio'n of the coil unit and defrostingarrangement with the casing of. the -coil unit removed-to display thecoil anddefrosting line:

Referring to-the drawings, there is shown in Figure 1 a refrigeratedspace 2 such as thestorage space. of'a warehouse designed tobemaintained at a temperaturebelow freezing. A penthouse 3 is placed onthe roof of the structure and is connected to refrigerated space 2 byopening .4 through which air is'drawn into the penthouse: and duct 5through which cooled'air is discharged into the refrigerated space tomaintain circulation of coldair therethrough.

In the penthouse 3 is placed a plurality of cooling coils 6 whichfunction as theevaporator of arefrigeration system (not shown). Thehigh*side of the -refrigeration system'is placed withouttherefrigeratedareaand isconnected to-the coils in the usualmanner; It willbe appreciated refrigerated brine may be passedthrough coils 6 orif'desired' direct eXpansioncoils-may beemployed. Fan 7 actuated by asuitable motortnotshown) serves'to draw-air from refrigerated-space 2.into the penthouse 3 passing the air through co-ils- 6 and thendischarging the cooled air through-duct 5 into the refrigeratedspace-:so that a continuous circulationoficooled air ismaintainedthroughout thev refrigerated area. An air-distribution duct (not shown)may be provided in the refrigerated space ifdesired to assureany-desired 'circulation of'cooled air therethrough: It will beunderstood while I havedescribed a plurality of cooling coils, theinvention'is applicable to a single coil.

A plurality of flapqdoors-S are provided at "the discharge side of' the.coils,6,-the doors being closed during a defrosting operationin order todiscontinue gravity-flow of air through the coils to the refrigeratedarea which might inadvertently raise the temperatureini-the refrigeratedspace. Below the coils is placed a drip pan-9 which serves to collectwater and meltedfrost from'the-coils.

An inclined drain pipe 10'eXtends downwardly fromthe drip panto a pointwithout penthouse 3.. Preferably the drain pipe .10 is closedexteriorlyof the penthouse 3 by a cap .11. It will be appreciated, if desired, aloop in drain pipeltlexteriorly of the penthouse may be pro-videdinsteadof cap 11. The: purpose ofathe .cap;or loop, of course, is toprevent.warm,moisture ladenedair' entering the drain pipe during therefrigerating operation-since the moisture from such air mightcondense,- formingice to.v prevent drainage through pipe 10..

A plurality of sets. of spray nozzles 12 are placedadjacent the top ofeach coil tospray waterthe-reover during a defrostingoperation.Referring to Figure 2, it will-be observed that spray. nozzles .13areprovided torspray water over. the underside of the coil 6 during. thedefrostingoperation. The. spraynozzleslZ areconnected to headers 14which, inzturn, are connected to pipe 15. Spraynozzles' 13 areconectedto headers*16which in turnare also. connected to pipe 115. The headers14, 16 are inclined so that water will flow backwardly therein to pipe15. Pipe 15 extends vertically so that water therein will flow downwardwhen supply of water is discontinued. Pipe 15 is connected to aninclined pipe 17, which extends downwardly to a point without therefrigerated space and is connected to a source of supply of water whichmay be, for example, a city water supply. A valve 18 is placed withinpipe 17 exteriorly of the refrigerated space. Valve 18 serves to controlsupply -of water to the defrosting arrangement. A drain pipe 19 isconnected to pipe 17 without the refrigerated space, a valve 20 beingplaced in pipe 19. When valve 2! is in an open position, water in pipe17 is free to drain therefrom so that the greater portion of the waterin spray nozzles 13, 12, headers 14, 16 and pipe 15 is free to flow in abackward direction without the refrigerated space and be discharged toany suitable drain.

Connected to pipe 17 between valve 18 and the point of connection ofdrain pipe 19 is a compressed air supply line 21, for a purposehereinafter explained. A valve 22 is placed in compressed air supplyline to control passage of compressed air therethrough. Line 21, ofcourse, is connected to any suitable source of supply of compressed airsuch as a compressor.

It will be appreciated that valves 18, 20, 22 may be manually orautomatically operated. Preferably, such valves are solenoid valves,electrically actuated.

Considering the operation of the system, the refrigeration system isstarted to cool brine. A brine pump (not shown) is actuated to pass coldbrine through coils 6, fan 7 serving to draw air from the refrigeratedspace 2 through the coils thereby cooling the air and to discharge thecooled air into the refrigerated area. Under these circumstances, frostcollects on the coils so that periodic defrosting of the coils isrequired for efficient, economical, operation. When it is desired todefrost the coils, opera tion of the fan is discontinued. Operation ofthe brine circulating pump is also discontinued. The flap doors on theair leaving side of the coils is closed. Cap 11 closing drain pipe isremoved to permit drainage of water and melted frost from the drainpipe. Valve 18 is then opened permitting supply of water through pipe17, pipe and headers 14, 16 to spray nozzles 12, 13 which serve todischarge the water over the coil surfaces to melt the frost therefrom.

After the frost has been substantially removed from the surfaces of thecoil, valve 18 is closed and valve 20 "is opened to permit water todrain from pipe 17, pipe 15,

headers 14, 16. Under some circumstances, of course, films of water mayform across the spray nozzle orifices. When it appears that water hascompleted drainage from pipe 17, valve 20 is closed and valve 22 isopened,permitting compressed air to pass from line 21 into pipe 17 andbe supplied to the spray nozzles and discharged therefrom so as to breakany water film formed across the spray nozzle orifices. Compressed airis discharged through the spray nozzle orifices for any short period oftime sufficient to assure that a film of water does not form across thenozzles. This film of water, of course, if permitted to form, wouldfreeze thereby preventing defrosting when the coils again require theremoval of frost from the heat exchange surfaces thereof.

Valve 22 is closed discontinuing supply of compressed air to the spraynozzle orifices. Cap 11 is replaced on drain pipe 10 and the flap doors8 are opened to permit air from the refrigerated space to be drawnthrough the coils. The fan is then started to circulate air through thecoils and the refrigerated space. The pump of the brine system isactuated to circulate cooled brine to the coils 6 in heat exchangerelation with air passing therethrough so that the system is againplaced in its refrigerating cycle.

While I have described this arrangement as employing a cooled brine forrefrigeration purposes, it will be understood that the coils may be, ifdesired, direct expansion coils connected directly to a refrigerationsys- The present invention provides a simple, economical, effectivedefrosting arrangement for coils placed in a refrigerated space. While Ihave shown the refrigerating coils placed in a penthouse connected to arefrigerated space, it will be appreciated temperatures in the penthouseare approximately the same as the tempera tures in the refrigeratedspace. In some installations, of course, the refrigerating coils will beplaced directly in the refrigerated space rather than in an areaconnected thereto.

The present invention permits the use of water to defrost refrigeratingcoils subject to the temperature of an area below the freezing point ofwater. To assure that no water remains in the Water lines during arefrigerating operation, positive means have been provided for assuringremoval of all water from the water lines subject to temperatures belowthe freezing point of Water. The present invention prevents theformation of a water film across the spray nozzle orifices, thuspreventing formation of ice in the spray nozzles which would prevent asubsequent defrosting operation.

While I have described a preferred embodiment of the invention, it willbe understood that the invention is not limited thereto since it may beotherwise embodied within the scope of the following claim.

I claim:

In a defrosting arrangement, the combination of a first compartmentadapted to contain articles to be refrigerated, a second compartment incommunication with said first compartment, a fan associated with saidsecond compartment adapted to induce an air stream from said firstcompartment through the second compartment and back into said firstcompartment, at least one evaporator coil located in said secondcompartment, said evaporator being in heat exchange relation with theair stream induced through second compartment, a plurality of spraynozzles operatively associated with -said evaporator so that fluidissuing from said spray nozzles will substantially cover the evaporatorsurface, a header operatively connected to said spray nozzles andadapted to supply a defrosting fluid to said spray nozzles, said headerpassing from said second compartment to points remote from said firstand second compartments, a drain valve located in said header remotefrom said second compartment, a line operatively connected to a sourceof defrosting fluid, a line connected to a source of compressed gas,said last mentioned lines being operatively connected to said headervalve means being located in each of said lines and being adapted toselectively pass defrosting fiuid or compressed gas through said header,said header being so disposed so that gravity will drain substantiallyall fluid from said lines through said drain valve when said valves insaid lines are in closed position, a drip pan disposed below saidevaporator to collect all defrosting fluid dripping therefrom, said drippan being connected to a drain line adapted to pass defrosting fluidfrom said second compartment, closure means associated with said lastmentioned drain line adapted to minimize heat transfer through saiddrain line into said second compartment, at least one damper memberbeing located in said second compartment, said damper member beingadapted to be closed during the defrosting process so as to restrict theflow of air through the second compartment during the defrostingprocess.

References Cited in the file of this patent UNITED STATES .PATENTS2,480,346 Watts Aug. 30, 1949 2,527,368 McGrath Oct. 24, 1950 2,583,271Mellion Jan. 22, 1952 2,607,202 Garland Aug. 19, 1952

